The present invention relates to a process for preparing fine zeolite particles, fine zeolite particles obtainable by the process, and a detergent composition comprising the fine zeolite particles.
Zeolite has been utilized for detergent builders as a water-softening agent owing to its ion-exchange properties. The ion exchange properties are greatly dependent on the primary particle size of the zeolite. Since zeolite having a very fine primary particle size is excellent in the ionic exchange speed, it has been known to exhibit a high deterging performance.
In addition, there have been known that the fine zeolite particles have the merits of having little deposition on clothes and reducing turbidity, so that the fine zeolite particles are useful as detergent builders.
As a process for preparing such fine zeolite particles, there are given examples in which synthesis is completed under specified feeding composition of the raw materials and reaction conditions (temperature and time), when zeolite is synthesized by mixing sodium aluminate with sodium silicate as disclosed in Japanese Patent Laid-Open Nos. Sho 60-127218 and Sho 62-275016. When very fine zeolite is synthesized by the process as described above, the process has to be carried out under certain restricted conditions in the feeding composition of the raw materials and the reaction conditions, so that there arise problems such as lowered productivity.
There has been reported that the particle size of zeolite is made very fine by adding a soluble hydrocarbon such as saccharose as disclosed in Japanese Patent Laid-Open No. Sho 60-118625. However, when the present inventors have applied this process to the synthesis of zeolite, an effect of reducing a primary particle size could not be found even when adding the soluble hydrocarbon as described above.
On the other hand, the alkaline earth metal is an element which can be easily substituted with Na in zeolite. Therefore, from the viewpoint of the function as an ion-exchangeable cation, there are many cases where the alkaline earth metal is considered to have the same value as the alkali metal. Japanese Patent Laid-Open No. Sho 55-116617 discloses that zeolite is utilized as an adsorbent having heat stability, wherein sodium in zeolite is partly substituted with an akaline earth metal.
However, there have not yet been any reports describing that an alkaline earth metal is intentionally and positively added during synthesis of zeolite, to give a product which exhibits an excellent function as a water-softening agent, nor any reports describing that the alkaline earth element is an essential element indispensable for making its primary particle size small.
In addition, there has been tried to make the particle size small from the viewpoint of preparation process. For instance, Japanese Patent Laid-Open No. Sho 62-46494 discloses that zeolite is mechanically pulverized by utilizing various kinds of mixing apparatus. However, there is much room for improvement from the viewpoints of the performance of the fine zeolite particles and the production efficiency.
An object of the present invention is to provide a process for efficiently preparing fine zeolite particles comprising synthesizing zeolite in the presence of an alkaline earth metal-containing compound and/or with controlling the preparation process of zeolite, thereby giving fine zeolite particles being composed of crystalline aluminosilicate, the fine zeolite particles having a fine average primary particle size, being excellent in the cationic exchange properties and the oil-absorbing ability, having a fine average aggregate particle size, and being excellent in the dispersibility; fine zeolite particles obtainable by the above process; and a detergent composition comprising the fine zeolite particles, the detergent composition being excellent in the detergency.
The above object and other objects of the present invention will be apparent from the following description.
Specifically, the present invention relates to:
[1] a process for preparing fine zeolite particles comprising reacting a silica source with an aluminum source in the presence of an alkaline earth metal-containing compound;
[2] a process for preparing fine zeolite particles comprising feeding for reaction an aluminum source and/or a silica source into a circulating line connected to a reaction tank;
[3] the process according to item [1] above, wherein the aluminum source and/or the silica source are fed for reaction into the circulating line connected to the reaction tank;
[4] fine zeolite particles obtainable by the process according to the process of any one of items [1] to [3] above; and
[5] a detergent composition comprising the fine zeolite particles of item [4] above.